Electronic apparatus



F 9 J. c. B ATCHELOR I ELECTRONIC APPARATUS Filed April 25, 1955 Patented Feb. 7, 1939 T UNITED STATES PATENT OFFICE 4 Claims.

able to use in cathode ray tubes and the like,

and more particularly, to a type of construction of such guns wherein features are involved which improve the ease andspeed of evacuation of tubes in which my gun is employed.

It is customary in the television and related arts to produce electron guns for use in cathode ray tubes comprising an electron emitting cathode, an apertured electrostatic control-element and an apertured accelerating anode, whereby electrons may be drawn from the cathode, controlled in quantity, collimated, focused and directed toward a fluorescent structure in a tube containing the electron gun. In such guns, it is customaryto employ a cylindrical control-element containing an apertured disc and mounted coaxially with a disc-like electron emitter. At a point along the axis of the control-element and remote from the cathode, a cylindrical anode containing one or more apertured discs is mounted in axially spaced relation to the control-element. In such electron guns it has been proposed to use a ceramic or other type of insulating ring 25 having an inwardly extending apertured flange, the ring portion having such an internal diameter as to snugly embrace the external diameter of the control-element and accelerating anode, and the inwardly extending flange having such a diameter as to axially abut the adjacent end portions of the control-element and accelerating anode. In such construction, it is clear that a chamber is produced enclosed by the cylindrical portion of the control-element, the apertured disc of the 3 control-element and an apertured disc of the accelerating anode, from which gaseous communi-. cation to a point exterior thereto is possible only through the apertures in the control and anode discs. 40 Moreover, when a plurality of apertured discs are used in the accelerating anode, for example, a second chamber is described by the anode cylinder and the apertured discs, and gaseous communication from the chamber is possible only through the small apertures in the discs.

Thus, in the conventional construction of electron guns, it is common to have one or more chambers which, during the period of exhaustion of a tube containing the gun, are exhausted relatively slowly because of the high impedance t gas flow of the apertures in the various discs. The presence of such high impedance to a gas flow is of particular dis-advantage during the step of outgassing such tubes when, by high irequency induction, electronic bombardment or other My invention relates to an electron gun adaptmeans, the electron gun is heated for thepurpose of dispelling entrapped gas from the physical parts of the gun. Such gas is evolved to a large extent from both the external and internal surfaces of the discs, cylinders and the like, and 5 therefore substantial quantities of gas areevolved within the chambers in the electron gun; such gases are removed only slowly because of the impedance of the apertures through which the gas must travel. Because of the slow rate of ex- 10 haustion of these chambers, the pressure within them rises to a value of the order of the vapor pressure of the gases entrapped under the condltions of entrapment, and consequently the outgassing process is appreciably retarded. 15

Still further, the electron emitting cathode is usually located adjacent and in close proximity to one of the apertures through which the gridanode chamber is being exhausted, and in the outgassing process, substantial damage can be done to the cathode by impact of the stream of gas passing through the control apertures as it strikes the cathode. This damage is particularly serious in cases when the outgassing process is accomplished by electronic bombardment from the heated cathode, or when, for any other reason, the cathode is maintained near, at or above operating temperature during the outgassing process.

In consideration of the foregoing, it is an object of my invention to provide an electron gun wherein easyegress is available to gas which is present within electrostatically enclosed portions of the electron gun.

In accordance with my invention, I have provided an electron gun comprising an electron emitting cathode, a control-element for controlling the number of electrons drawn from the cathode, and at least one accelerating anode for extracting and collimating electrons from the cathode to produce an electron beam, and having the anode and control-element rigidly supported by an insulating member so constructed as to allow easy egress to gas from the volume enclosed between the control-element and anode. Further, in accordance with my invention, I have provided an electron gun which is composed of woven wire mesh or finely perforated metal having a fineness of perforation such that easy penetration of the metal by gas is possible, yet' electrostatically the perforated portion is substantially a solid plane surface.

In order to make possible a more complete description of my invention, attention is directed to'the accompanyingdrawing of which Figure 1 is a sectional view of a portion of a cathode ray tube in which is mounted an electron gun made in accordance with my invention; Figure 2 represents a plan view of an insulating member adaptable to my invention; Figure 3 represents a sectional view of the insulating member shown in Figure 2 taken along the line 3 in the direction designated by the arrows.

Referring to Figure 1, the electron gun generally referred to by the reference numeral I is mounted on the stem 2 which is in turn carried in and coaxial with the neck 3 of a cathode ray tube which may be of any appropriate size and shape and of which only the neck portion 3 is shown. Carried on the lead-in wires 4 is a heater 5 which may be a double tungsten spiral coated with ceramic insulating material, and surrounding the heater is a cathode sleeve 6, one end of which is closed by the electron emissive disc I. The sleeve 6 may consist of a seamless tube of metal of suiliciently high melting point such as tantalum or nickel, and the disc 'I may be made of a metal such as nickel or platinum and may have a thin film of electron emitting material, such as a mixture of barium and strontium oxides, on its external surface. The sleeve 6 is mounted upon and in electrical communication with one of the lead-in wires 4.

The metallic cylinder 8 comprising a solid portion 9 and a perforated portion I0 is mounted on the support wire II and lead-in wire I2 and is coaxial with the emitter disc I. A centrally perforated control disc I3 is mounted at or about the junction between the portions 9 and I0 of the cylinder 8 and, further, mounted with the aperture I4 adjacent and parallel to the emitter disc I. Further, at the terminating circle of the cylinder 8 remote from the disc I3 is provided a solid metallic ring I5 having a smoothly cut or machined terminal circle to provide a termination of the cylinder 8 in a uniform circle I6 lying in a plane normal to the axis of the cylinder 8.

A cylindrical anode I1 is provided comprising a solid portion I8 and a perforated portion I9. A solid metallic ring 20 is provided similar to the ring I5 in order to provide a termination of the perforated portion I9 in a uniform circle 2| in a plane normal to the axis of the anode I1. Further, a centrally perforated disc 22 is mounted in the anode I! in a manner such that the external plane of the disc 22 is coincident with the plane described by the terminal circle of the ring 29, and a second centrally perforated disc 23 is mounted in the anode I I at or about the junction between the portions I8 and I9.

The description from this point will refer to Figure 1, but greater detail may be appreciated by referring simultaneously to Figures 2 and 3. A ceramic or other insulating ring 24 is provided with an internal diameter 25 such that it will snugly embrace the rings I5 and 20 and, further, provided with an inwardly extending annular ring 26 having plane parallel opposite faces 21 and 28 against which the plane termini of the rings I5 and 20 abut. Thus, by means of the ring 24, the anode I! may be mounted in fixed relation to the metallic cylinder 8 and maintained in fixed, spaced relation to and coaxial with that element. In order to maintain the annular ring 26 firmly in compression so that the relation between the anode I! and the cylinder 8 may be maintained, the insulating tension members 29 are provided, each comprising a glass bead 30 having the oppositely extending, insulatedly separated wires 3| and 32 of which the wire 3I is attached to the cylinder 8 by spot welding or other suitable means and the wire 32 is attached to the spring 33 which is maintained in tension and attached to the anode I1 at the point 34. Thus, the anode I! is drawn firmly by the springs 33 against the ring 26, and yet during periods of changing temperature, and consequently expansion, the members 29 allow and absorb the motion of expansion of the metallic parts, and the springs 33 do not allow a permanent distortion which would otherwise appear to cause a separation between the adjacent termini of the rings I5 and 20 and the surfaces 21 and 28 of the ring 26, which would result in probable misalinement of the components of the gun.

Referring now to Figures 2 and 3, I have provided in the ring 24 a plurality of openings 35 extending radially through the ring 24 and through which relatively easy passage of gas is allowed. With the ring applied to my electron gun as shown in Figure 1, gas generated or existing within the space described by the apertured discs I3 and 2|, the portion ID of the cylinder 8, and the ring 24 is now provided with a multiplicity of paths for egress including the aperture I4 in the disc I3, the aperture 36 in the disc 22, the openings 35 in the ring 24, and the perforations in the portion ID of the cylinder 8. Similarly, gas may find egress from the volume enclosed by the discs 22 and 23, and the portion I9 of the cylinder I! through the aperture 36 in the disc 22, the aperture 31 in the disc 23, and the perforations in the portion I9 of the cylinder I1. Thus, I have provided an electron gun, from the interior portions of which gas may be exhausted with greater case than was possible in guns prior to my invention, and this has been accomplished without modification of the electrical characteristics of the gun.

It may be seen that my invention is applicable to any electron gun wherein constructional components of the gun cooperate to produce a confined portion from which gas may be exhausted only with difiiculty.

I claim:

1. In a cathode ray tube, an electron gun comprising an electron-emissive cathode, a controlelement and anode structures comprising coaxial tubes supported in axially spaced relation and each provided with an apertured disc, the tube constituting said control-grid. structure having a skirt portion extending beyond the associated disc with its edge in close proximity to the anode tube, said skirt portion consisting of perforated metal.

2. A cathode ray tube comprising an envelope having a press, an electron-emissive cathode, a control-element structure comprising a metal tube containing a centrally perforated control disc, an anode structure comprising a metal tube containing at least one centrally perforated disc, a plurality of paths whereby gas may be exhausted from the volumes described by said tubes and said discs, an insulating member between said control-element and said anode so arranged and constructed as to hold said control-element and said anode against relative lateral displacement, a conductor sealed through said envelope and electrically yieldably connected to said anode, and a plurality of yieldable tension members extending between said control-element and said anode, whereby said control-element and said anode are held against relative axial displacement.

3. A cathode ray tube comprising an envelope 7 having a stem, an electron-emissive cathode, a control-element and an anode, conductors sealed through said stem and supporting said cathode and control-element, a gas-permeable insulating member between said control-element and said anode so arranged and constructed as to hold said control-element and said anode against relative lateral displacement, a conductor sealed through said envelope and electrically yieldably connected to said anode, and a plurality of yieldable tension members extending between said control element and said anode.

4. A cathode ray tube comprising an envelope having a press, an electron-emissive cathode, a control-element structure comprising a metal tube containing a centrally perforated control disc, an anode structure comprising a metal tube containing at least one centrally perforated disc, an insulating member between said controlelement and said anode so arranged and constructed as to hold said control-element and said anode against relative lateral displacement, a conductor sealed through said envelope and electrically yieldably connected to said anode, and a plurality of yieldable tension members urging said anode toward said control-element whereby said insulating member is maintained in compression and said control-element and said anode are held against relative axial displacement.

JOHN C. BATCHELOR. 

